As more and more information is moving into electronic form, encryption is becoming more common. One prior art method of encryption is public key encryption, an encryption scheme in which each computing device or person is assigned to a pair of keys, called the public key and the private key. Each person's public key is published while the private key is kept secret. As can be appreciated by one of ordinary skill in the art, public-key cryptography can be used for authentication (digital signatures) as well as for privacy (encryption). Messages are encrypted using the intended recipient's public key and can only be decrypted using the recipient's private key. Messages are signed using the sender's private key and can only be decrypted using the sender's public key. Other encryption schemes, such as symmetric key encryption also rely on the use of cryptographic keys (random bit sequence). By the use of cryptographic keys, two users or devices can make their messages to each other undecipherable by an eavesdropper, and successfully distinguish legitimate messages from modified ones by means of informationally secure mathematical authentication methods.
As can be appreciated by one of ordinary skill in the art, the generation of cryptographic keys should be unpredictable, truly random, and in some situations the keys should not be reused. As can be appreciated by one of ordinary skill in the art, there are many methods for generating security keys. In one existing practice, key codes are generated by measuring the typing speed and cadence (keystroke dynamics) of a person using a computing device. In such prior art systems, the typing speed and time between keystrokes are measured over an extended period of time. The measured values are then used to generate codes for a cryptographic key. While this technique is generally accepted in the industry as one method for generating a generally random key, this prior art method is not useful for stand-alone computing devices that are not operated by user.